1. Field of the Invention
The present invention is directed to a tightening tool for straps of the type used as cable, hose and duct clamps and pertains more particularly to a tool adapted to tighten cable ties of the type shown in Orban U.S. Pat. Nos. 3,368,247 of Feb. 13, 1968 and Caveney 3,537,146 of Nov. 3, 1970, as well as to steel strap fasteners.
2. The Prior Art
Cable or strap fasteners of the type of the above referenced patents comprise elongate plastic straps having an anchoring buckle at one end. Such fasteners are in widespread use and typically include mechanism within the eye of the buckle, such as a pawl or the like, which cooperates with ridges or teeth formed on the strap to permit the strap freely to be drawn through the buckle in a first or tightening direction but prevent return or retractile movement of the strap through the buckle.
While it is feasible manually to tighten straps of the type described about bundles of cable or wire where high pressures are not required, straps are frequently used in the manner of clamps, i.e. are encircled about a hose or fabric wrapping which has been sleeved over a pipe or manifold. In such cases it is highly desirable to tighten the strap down with a high degree of tension so as to eliminate leaks between the hose or wrapping and the encircled pipe or duct. In order to effect tightening of the strap numerous tightening devices have been suggested. Representative examples are shown in Caveney U.S. Pat. Nos. 3,169,560, Feb. 16, 1965; 3,254,680, June 7, 1966; 3,645,302, Feb. 29, 1972; 3,661,187, May 9, 1972; 3,946,769, Mar. 30, 1976; and 3,976,108, Aug. 24, 1976. Other references of similar nature could be cited.
The noted patents include a fixed member which bears against the buckle of the strap and a movable member adapted to grip the teeth of the strap. When the movable member is shifted in a first or tightening direction, the strap is drawn through the buckle. The devices include a pawl which, on a return stroke, release the strap so as to permit free movement between the strap and the tightening device until the tripping mechanism again is shifted to a position adjacent the buckle.
Devices of the type described typically employ a toothed pawl which is spring biased into contact with the tooth section of the strap to provide the necessary gripping of the strap.
A disadvantage of all such devices heretofore known is that the same are adapted to accommodate straps of only a limited thickness range. If, for example, a thin strip is attempted to be used with a tightening device intended to be used with thicker strips, little or no gripping force would be generated, with the result that attempts to tighten the strap would be ineffectual or would result in stripping the teeth from the strap due to inadequate meshing of a sufficient number of pawl teeth with the teeth of the strap.
In an application filed on Mar. 5, 1984 in the name of Charles Giannone and accorded Ser. No. 586,335, entitled Cinching Clamp Device and Method of Attachment there is disclosed a strap formed of thin metallic material having transversely directed spaced teeth or ridges. No known tightening device is capable of use both with the thicker cable ties as represented by the art hereinabove set forth and a thin steel strap as represented by the above referenced application.